Hi. I traveled in and out of the Osceola station fairly regularly between 2014 and February 2018. I left my truck there for 10 days or more several times. It is paved and well lit (part of a renovation project completed in sometime 2016, IIRC.)
I never had any trouble, nor did I hear of anyone else having any problems leaving their car there. In my new experience, the intrepid station volunteer was there everyday, rain or shine (or blizzard, one time!) 20-30 minutes before the scheduled arrival time, regardless of delays. I would generally mention to her that I was leaving my car. I felt that there wasn’t much that happened in or around the station that escaped her eagle eye!
Twenty, or so, spaces does sound about right. But, in all that time, I never saw it completely full. Hope that helps.